1. Field of the Invention
The present invention relates to a novel Pseudomonas fluorescens bacterium and variants thereof, and a material for controlling a plant pathogenic fungus, a plant growth promoting material and a compost comprising the above bacterium. More specifically, the present invention relates to a Pseudomonas fluorescens bacterium having an antagonistic property against plant pathogenic fungi of the genera Pythium, Rhizoctonia, Sclerotinia and Gaeumannomyces, growing well in the rhizosphere of a plant to sufficiently reveal the antagonistic property against the pathogenic fungi and being able to promote the growth of the plant by promoting the elongation of the root system and leaves of the plant, and also relates to a material for controlling plant pathogenic fungi, a plant growth promoting material and a compost comprising the above microorganism.
2. Description of the Prior Art
Lawn grass planted in golf courses and the like suffers a great damage from various kinds of lawn grass pathogenic fungi. Specifically, pythium red blight caused by Pythium aphanidermatum, spring dead spot caused by Pythium vanterpooli, brown patch caused by pathogenic fungi of the genus Rhizoctonia such as Rhizoctonia solani, dollar spot caused by pathogenic fungi of the genus Sclerotinia such as Sclerotinia homoeocarpa, take-all patch caused by pathogenic fungi of the genus Gaeumannomyces such as Gaeumannomyces graminis and the like may be cited for example.
As a means to control pathogenic fungi of plants such as lawn grass, application of drugs such as agricultural chemicals, selection of a variety resistant to pathogenic fungi and the like have been performed conventionally. In particular, application of drugs has been widely practiced. However, this method has caused various problems e.g., accumulation and remaining of drugs in human bodies and other organisms, stimulating smell, inflow and infiltration of drugs into rivers and underground water, destruction and pollution of natural environments such as destruction of ecosystems; thus, this method has become a big social problem.
In the method of selecting a variety resistant to pathogenic fungi, the variety of a plant to be grown is restricted and very often the growth environments and soil are not necessarily suitable for that variety.
Also, compound fertilizers have been used abundantly to promote the growth of plants. However, although compound fertilizers act quickly, they cause problems such as poor growth or withering due to inappropriate concentration of the fertilizer, infertilization of soil due to repeated application, environmental pollution and the like. A plant growth promoting material which does not cause such problems and which can replace compound fertilizers is needed.